The present invention relates to a coupling for flexibly joining pipe parts together in the exhaust systems of motor vehicles, with the coupling including at least one flexible pipe part such as a corrugated pipe, a metal hose or the like, having support parts, joining the ends of the flexible parts, for damping members placed around an outside of the coupling.
A coupling for joining two pipes at an exhaust outlet of the engine and the exhaust system of a motor vehicle is proposed in Offenlegungsschrift No. 2,838,990. Such coupling makes it possible to provide a large degree of relative motion between the engine and the exhaust gas system thereby increasing the life of the exhaust system. In the known coupling, two connection flanges, placed at the connection ends of a single flexible pipe or of an interlocking strip pipe, have bolts extending therethrough and are clamped by the same using a spring element.
A disadvantage of the above proposed coupling resides in the fact that the design is generally complex, and for this reason, likely to be damaged. A further disadvantage resides in the fact that although, in this known design, relative motion of the engine and of the exhaust system may be taken up, because, by virtue of the arrangement of the spring elements, the spring elements are not decoupled so that vibrations of the engine may well be transmitted to the exhaust system where they may cause noise and an overly high rate of wear. Although it has been suggested to propose additional damping members, possibly combined with the spring element, this would be only an attempt at using the theoretical purely resilient damping properties of a spring. Because of the use of a spring element, with its resilient and resonant properties, in this system when an attempt at cutting out such properties by the use of friction acting on the element, it is not possible to achieve a decoupling effect and there is no question of the best possible suppression of the noise made by the exhaust system.
The aim underlying the present invention resides in providing a simple, sturdy and trouble-free unit for flexibly joining pipe parts of an exhaust system of a motor vehicle.
A further object of the present invention resides in providing a joint means for stopping transmission of the motion of the engine of a motor vehicle to parts of the exhaust system.
A still further object of the present invention resides in ensuring the best possible suppression of exhaust system noise. In accordance with advantageous features of the present invention, a joint or coupling system is provided wherein the support parts are placed so as to overlap each other on an outer side of the pipe part, with the parts forming housing-like pockets that may be moved relative to each other, which pockets have damping cushions of pressed metal wire.
By virtue of the present invention, it is possible to eliminate the use of a spring element, in the true or more limited sense of the word, and to use a highly effective conventional damping cushion which has so far only been used for other purposes. More particularly, by virtue of the features of the present invention, it is possible to provide a damping cushion with the elements thereof made of, for example, a pressed metal wire in the form of a pressed wire cloth, pressed wire grid, randomly pressed wire or the like, which whatever the working condition, when bent out of the normal form, will return to an unstressed position more or less asymptotically after being deformed by the force acting thereon, with the motion into the unstressed condition taking place with little or no resilient effect in the sense of overshooting beyond the unstressed position, that is, after being stressed and released in the opposite direction.
In fact, unlike the case of the true spring, the idea behind the present invention resides in eliminating the use of any spring, as regularly used in the prior art, and using, in place thereof, a special-purpose damping cushion or shock adsorbing pad. Unlike the case of springs such as, for example, spiral springs, such cushions have the useful property of having a highly progressive strain-stress curve. The kinetic or oscillation energy is quickly turned into heat, that is rapidly conducted away because of the high conductivity of the cushion metal, namely, wire, and the air spaces therein. Whereas the exhaust gas will be at a temperature of up to 1100.degree. C., within the damping cushion, the temperature will be at a level of 200.degree.-250.degree. C. so that not even damage to the material by overheating is to be feared.
A further point with this design is that it is possible to do without a complex structure using tightening nuts for keeping bolts, that are able to be moved in relation to the connection pieces, in place. The support parts forming housings on the pockets are in fact more specially all fixedly joined to the ends in question of the flexible pipe part, a useful effect being produced if one part of the support parts is formed by stamping out and bending back parts of a connection pipe sealingly joined with one end of the corrugated pipe. For this reason, the joint system of the present invention may be more readily manufactured, from the point of view of a production engineer, than conventional corrugated joint systems. The decoupling structure of the invention makes use of the best possible selection of different features for meeting the design needs of an exhaust system to be used in a motor vehicle. Its mobility in a low frequency range is great enough even at a high amplitude, while the joint has a powerful damping effect in the acoustic oscillation range in which the amplitude is low. The construction of the present invention makes it possible for lighter exhaust pipe systems and mountings to be used.
The construction of the invention makes it possible, dependent on the needs, for tension, compression, angular and lateral loads on the corrugated pipe to be absorbed. In this case, in preferred forms of the invention, the one or the other damping cushion, placed one after the other in the axial direction, is loaded in an axial direction by a compression force. It is furthermore possible for a damping cushion to simply be placed between two bearers, that may in addition be fixedly joined, as, for example, by welding, bonding or the like, with the support parts, such damping cushion then being additionally capable of being loaded by tension forces.
If desired, it is then possible, within the framework of a further development of the present invention, to have a number of support parts placed one after the other for the damping cushion, with the support parts being rigidly joined, in turn, with one and then with the other end of the pipe part.
To maintain the damping cushions in place, radially, the damping cushions are placed in a housing with housing-like pockets, that are formed by the support parts, with the pockets having bearer faces for the damping cushions. In this case, the design is such that the support parts have generally radially running end faces as bearers for the damping cushions, taking the form of supporting parts placed at the ends in question of the pipe part. It is furthermore possible for at least one end wall of a housing-like pocket for the damping cushion to be formed by a ring part placed on a rod running generally through the middle of the cushion, the rod running freely at least through another support part adjacent thereto. In this respect, the damping cushions have holes in the middle thereof with the rod running therethrough, the rod being fixedly joined to a supporting part. As part of a still further development of the invention, at least one supporting part has a radially running, two-layer cupped part, whose two end faces are in the form of two separate bearer parts.
The alignment of the pocket-forming support parts and the damping cushions seated in them may be in keeping with the main direction of the components of the motion that are to be taken up. It is possible, in order to generally absorb axial motion, for the support parts to have end faces such that lines normal thereto are generally axial for use as bearers for the damping cushions, that are formed at the ends in question of the pipe part.
It is furthermore possible, in place of this, for the support parts to have end faces (so placed that the lines normal thereto are generally radial in direction) designed as supporting parts for the damping cushion, that are formed at the ends in question of the pipe part for the purpose of damping radially directed motions such as angular motion or lateral motion. To the degree that, in addition to damping motion in the main direction of motion in question, forms of motion in other directions are to be absorbed, a changed form of the damping cushion may be used in keeping with the motion to be absorbed or damped. Whereas, in the case of radially symmetrical damping cushions, it is not possible for crossways forces in a plane normal to the main axis of the system to be absorbed, and such forces will only be responsible for a twisting effect, in a preferred form of the invention, the damping cushions are not made radially symmetrical. This makes it possible for crossways or transverse forces to also be absorbed. Motion acting centrally on the damping elements but at the same time in a sideways direction may be absorbed inasfar as the end faces of their central part are angled back towards their edges so that more specially between the end faces and the outer faces there will be a right angle. While, on the other hand, the form of the damping cushion may be produced as desired by clamping or pre-stressing after they have been fixed in place in the pockets formed by the support parts, in keeping with a preferred form of the invention, the damping cushions are prestressed into the form of the housing-like pockets. Great trouble is experienced in the case of such exhaust systems for motor vehicles inasfar as there is relatively little space on hand near the exhaust system, at least in certain directions. While it is possible, for the damping cushions to be placed radially about the flexible pipe part, the amount of space is frequently not large enough directly over the flexible pipe part, because the flexible pipe part, if in the form of, for example, a bellows, takes up quite a bit of space in the radial direction, inasfar as the waves of the bellows generally have a larger radius than the radius of the pipe parts of the system. It is for this reason that, in keeping with a further form of the invention, the damping cushions are placed next to the flexible pipe part in such a way that they are axially out of line with each other in the axial direction. More particularly, inasfar as the main axis of the normals to the faces of the support parts is radially in direction, it is furthermore possible according to the invention for a support part to have a bridge piece for one of the damping cushions, such bridge piece being seated on the outer face of the flexible pipe part, whereas, the other support part is seated on a part joined with the other end of the flexible pipe part and takes the form of a pipe part running out past the end of the flexible pipe part. Inasfar as twin or double pipe systems are used, the support parts may be placed with the cushions generally linearly in a single plane with the pipe parts next thereto, if there is enough space in this direction but not enough space in the direction at a right angle thereto. If the amounts of space are different, it is however furthermore possible for the support parts with the damping cushions to be placed to the side between the pipe parts so that, in each case, they are placed right over the flexible pipe parts or out of line in an axial direction. As a point the damping cushion does not have to be pre-stressed or to be under a stress when put into position. However, to the degree that such prestressing effect is desired, such stress may be matched or adjusted in the right way. In one form of the invention, a bearer face of one support part may be formed by one threaded washer or disc screwed into a threaded bushing. As part of another possible design, in at least one end face of a support part, there are a number of nose pieces running out symmetrically from the outer edge thereof and, between the end face of the support part and the damping cushion, there are openings equal in number to the number of nose pieces, with the diameter of the openings changing from one opening to the next one and the greatest diameter being generally equal to the outer size of the nose pieces; and the washer may be adjusted from the outside for changing the angular position thereof.